1. Field of the Invention
The present invention generally relates to production of electronic products, and more particularly relates to production of hollow-package type electronic products, each of which has a hollow space for accommodating an electronic component therein.
2. Description of the Related Art
Among electronic products, there are electronic packages, each of which includes a plate-like mount, an electronic component mounted on the plate-like mount, a plurality of leads electrically connected to the electronic component, and an enveloper for encapsulating the electronic component together with inner lead sections of the leads, to thereby protect the electronic component from the outside. The lead elements pass and extend through the enveloper, and an outer lead section of each lead serves as an electrode terminal for the electronic package.
When the electronic component includes a high power transistor, such as a power MOSFET or the like, which is frequently utilized in an analog amplifier or the like, a large amount of heat is generated from the electronic component during the operation of the electronic package. Thus, when the electronic component includes the high power transistor, the plate-like mount, on which the electronic component is mounted, is formed as a heat radiating plate, which is made of a suitable metal material, such as copper, brass, stainless steel, aluminum or the like, to thereby facilitate radiation of heat from the electronic component.
When the envelopes for encapsulating the electronic component is formed of a suitable thermosetting resin, the electronic package is frequently called a resin-sealed package. Conventionally, the resin-sealed package may be manufactured as explained below.
The electronic component is mounted on and adhered to the plate-like mount or heat radiating plate, such that electrode pads of the electronic component, provided on a bottom face thereof, are electrically connected to the heat radiating plate. Also, the electronic component is provided with electrode pads provided on a top face thereof, and the respective electrode pads are connected to the inner lead sections of the leads through the intermediary of bonding-wires. Thereafter, the electronic component and the inner lead sections are put in a molding cavity of a metal mold, and then sealing-resin is injected into the molding cavity, whereby the electronic component and the inner lead sections are enclosed with and encapsulated in the molded resin, with the outer lead sections of the leads being protruded from the molded resin as the electrode terminals. Thus, in the resin-sealed package, the electronic component and the inner lead sections are in direct contact with the molded resin.
When the electronic component includes the high power transistor, it generates a very large amount of heat during the operation of the resin-sealed package, and thus the molded resin may be subjected to deterioration and exfoliation. In this case, the characteristics of the resin-sealed package are changed, resulting in a decline in the operational reliability.
Also, as stated above, since the molded resin is in direct contact with the electronic component and the inner lead sections, it may serve as a dielectric layer, resulting in production of a parasitic capacitance. Accordingly, due to the interference based on the production of the parasitic capacitance, the frequency characteristics of the resin-sealed package may be deteriorated in a high-frequency band of more than 1 GHz. In particular, the deterioration of the high-frequency characteristics causes serious problems in microwave applications of the resin-sealed package.
A hollow-package type electronic product is well known as an electronic package which is not subject to the above-mentioned problems involved in the resin-sealed package, and is frequently represented by a ceramic package, a metal package or the like. Also, the hollow-package type electronic product is disclosed in, for example, Japanese Laid-Open Patent Publications (KOKAI) No. HEI-06-069366, No. 2000-183204, No. 2001-196488 and No. 2001-044228.
For example, in producing the hollow-package type electronic product, the electronic component is mounted on and adhered to the heat radiating plate, such that the bottom electrode pads of the electronic component are electrically connected to the heat radiating plate. Then, a surrounding wall member is securely attached to the heat radiating plate such that the electronic component is encompassed by the surrounding wall member. Thereafter, the leads are put on tops of opposite side wall sections of the surrounding wall member, and the respective top electrode pads are connected to the inner lead sections of the leads through the intermediary of bonding-wires. After the electrical connections of the top electrode pads to the inner lead sections of the lead are finished, a lid member is securely adhered to the top end face of the surrounding wall member, resulting in production of the hollow-package type electronic product in which the electronic component is accommodated and sealed in the hollow space defined by the surrounding wall member and the lid member, with the outer lead sections of the leads being protruded from the interface between the surrounding wall member and the lid member.
Note, although both the surrounding wall member and the lid member are made of either a suitable ceramic material (ceramic package) or a suitable metal material (metal package), another suitable material, such as thermosetting resin, a composite rein material or the like may be used for the surrounding wall member and the lid member.
As stated above, since-the electronic component is accommodated and sealed in the hollow space defined by the surrounding wall member and the lid member, the hollow-package type electronic product is not subject to the above-mentioned problems involved in the resin-sealed package. Nevertheless, conventionally, it has not been proposed how to produce a large quantity of hollow-package type electronic products efficiently and at low cost.